A CLOSER LOOK: CONSTRUCTION OF STATIONS AND SHAFTS
Characteristics of the stations
The criteria in designing the stations, based on experiences that now consider underground stations as places for meeting and not just transit, enlivened by commercial and cultural activities as well as services, are as follows:
- Public safety.
- High-tech systems (ventilation, air barriers, sprinklers).
- Clean and welcoming.
- Immediacy of information.
- Architectural decor.
- Functionality of paths identified by signs and markings on the pavement for the visually impaired.
- Absence of architectural barriers; there will also be “tactile” paths for the blind, with “relief” signage.
The type of stations varies with respect to the characteristics of the city neighbourhoods traversed, while maintaining a strong exterior and interior formal identity to make them immediately identifiable.
The lobbies will accommodate restrooms, automatic ticketing and, where possible, commercial, exhibition, and recreational establishments.
The electronic entrance and exit gates will be placed between the lobbies and the station platform. The stations are located between the two single-track tunnels in which the Line C trains travel.
The Teano station is an exception for Line C, with its station platforms one on top of the other to facilitate the introduction of the Line C1 route, the north-eastern extension towards the Line B Ponte Mammolo station (project that is not part of the current contract assigned to Metro C S.c.p.A.).
In all stations, for the passengers’ safety, platform screen doors are installed that open, upon the trains’ arrival, simultaneously with the train doors.
Construction of the stations
PHASE 1 – DELIMITING: during this phase, the work site’s actual introduction into the urban fabric takes place. First, the area needed to accommodate the service structures and the excavations is limited to traffic. The station delimiting works start with the performance (where necessary) of support works to stabilise the terrain around the work site; generally these are piles or minipiles inserted into the subsoil.
Once the pre-existing structures are secured, the diaphragm walls, the “box” walls in reinforced concrete that will contain the station, are built.
PHASE 2 – ROOF: with this crucial phase, the work site begins to shrink in size.
The earth enclosed within the perimeter of the diaphragm walls is excavated down to the depth needed to create the roof slab, which will be the station’s future ceiling. Steel cages are assembled in the excavation, constituting the slab’s reinforcement; then the concrete is cast. The characteristic of the slab is the hole, an opening in the concrete layer, from which the earth begins to be excavated, and which will then allow men, equipment, and materials to access the work site’s underground levels. Once the slab is completed, the work site area can be restricted around the hole to allow the underground works to continue while restoring the road to its habitual use. Moreover, the use of this technique, called “Top-Down,” makes it possible to contain both the noise and the dust the work site produces, because the excavation takes place underground.
PHASE 3 – UNDERGROUND EXCAVATION: the station’s underground levels are excavated. At pre-established depths, intermediate slabs are made. The procedure used is the same as that used for the roof slab. For the intermediate slabs, too, a hole is left to allow the work site to move down to the level beneath. The final slab to be made is the bottom slab, upon which the tracks in the station rest.
REVERSAL: this operation involves work site where the Top-Down technique is used in large areas, or areas with major traffic volumes, for which it is impossible to occupy the whole road surface. The working phases are exactly those described above; the only difference is that they are performed only on one half (or on a smaller portion) of the area affected by the works. Once the initial delimiting and roofing phases are performed, the work site is disassembled and “reversed” in mirror image on the other half of the road – with the phases starting from zero and then continuing with the underground excavation phase.